Six-Leg Single-Phase Multilevel Rectifier Inverter: PWM Strategies and Control

This paper discusses a rectifier inverter composed of two three-leg converters with equal and unequal dc-links voltages connected in series. The operation with equal dc-links voltages divides equally the voltages in each converter. On the other hand, the operation with unequal dc-links voltages increases the number of voltage levels and contributes to reduce harmonic distortion and power losses. Space-vector and level-shifted techniques are discussed. The balance of separated dc sources using redundant voltage vectors is addressed in this paper. A closed-loop controller is used to control the average value of the dc voltages. Simulation results compare power losses and harmonic distortion of three-leg and six-leg topologies. Experimental results are provided to validate the feasibility of the system.